The present invention pertains to fluid filters and, more particularly, an end cap relief valve mechanism for a fluid filter.
Ordinarily, fluid filters, such as oil filters, are provided with relief valves in order to bypass the filter element in the event that the oil filter becomes clogged during use. The oil filter usually comprises a housing or shell having an open end closed by an end plate. The end plate usually contains one or more inlet openings and an outlet opening. Within the housing is an annular filter media pack. Normally, there is a valve comprised of a valve seat, a valve member and a spring for biasing the valve to the closed position disposed within the housing. The valve is commonly secured to the filter media pack.
Takahara U.S. Pat. No. 5,759,351 shows an oil filter having a plate spring for biasing a filter pack within a housing. When the filter pack becomes clogged, the pressure in the housing increases and the relief valve opens to keep the flow rate of the oil supplied to the engine. The filter pack does not include end caps and the relief valve of Takahara is structurally different from that of the applicant.
Sundhohn U.S. Pat. No. 5,019,251 discloses a filter having a relief valve mechanism with a spiral spring that is relatively bulky.
Cantoni U.S. Pat. No. 4,885,082 reveals an oil filter with a multi-component pressure relief valve having a bulky return spring. The prior art relief valves, as exemplified by those shown in the cited references, are constructed separate from the end cap, and proper positioning of the valve within the housing of the fluid filter was sometimes difficult and/or time consuming. The prior relief valves were relatively bulky and occupied considerable volume within the housing of the oil filter. Consideration was given to reducing the number of parts of the valve in order to reduce the cost and to enhance positioning of the valve and facilitate assembly of the fluid filter.
Further, when an engine is manufactured there are usually trace amounts of core sand and machining debris left within the engine from the manufacturing operation. The core sand and metal debris is very abrasive and must be removed as quickly as possible to prevent damage to the engine. This sand and debris can find its way into the engine oil. The engine oil needs to be cleaned prior to being pumped to various places in the engine. The oil filter should accomplish this cleaning operation and is usually successful in removing the sand and debris contaminants. Unfortunately, the first time the engine is started the oil filter bypass valve may open momentarily due to high differential pressure and the contaminants would not be filtered. If the initial bypass valve opening could be delayed a higher percentage of the contaminants could be removed.
An object of the present invention is to provide an improved fluid filter having a relief valve mechanism formed in part by an end cap, which overcomes difficulties and disadvantages of prior fluid filters.
Another object of the present invention is to provide an improved fluid filter that incorporates a relief valve mechanism as a part of an end cap to provide a relief valve mechanism that is compact, has a low profile and is less costly than prior relief valve mechanisms, thus allowing the fluid filter to be shorter, yet have the same filtration and flow characteristics as prior taller fluid filters, and which is capable of removing core sand and metal debris contaminants during initial operation of the engine with which the fluid filter is used.
Yet another object of the invention is to provide an improved fluid filter having a housing that incorporates an end cap and a spring that are operationally interengaged for controlling fluid flow and provide a relatively flat profile, together with temperature responsive means for holding the end cap and spring interengaged until the fluid temperature in the housing reaches a predetermined temperature and pressure, at which time fluid flow is permitted, whereby contaminants are removed from the fluid during initial operation of the engine with which the fluid filter is used.
Other objects and advantages of the present invention will be made more apparent in the description which follows.
A fluid filter, for example, an oil filter comprises a housing that is open at one end and closed at the other end by an end plate. The end plate has at least one inlet opening and one outlet opening therein. Filter media is disposed in the housing. An end cap is provided at each end of the filter media. An anti-drain back valve, disposed between the end plate and an end cap of the filter media adjacent the end plate, cooperates with the inlet opening to prevent the back flow of oil there through in use. The end cap remote from the end plate has at least one opening in the central portion thereof. A spring cooperates with the end cap remote from the end plate to close the opening in the end cap to fluid flow and is responsive to the pressure within the housing to open the flow path when the differential oil pressure in the housing exceeds a predetermined value. The end cap remote from the end plate and the spring comprise a relief valve mechanism. The spring also functions to load the filter media and to retain the anti-drain back valve in position between the end cap adjacent the end plate and the end plate. The spring is provided with spaced projections which maintain a flow path should the spring be flattened against the interior of the housing and thereby permit flow of oil around the spring to permit desired operation of the relief valve mechanism. The spring and the end cap remote from the end plate are constructed and arranged to provide an end cap relief valve mechanism that has a flat profile and occupies little more space than the end cap alone. A temperature responsive means is provided between the end cap and the spring to hold the parts until a predetermined temperature of oil is attained. Thereafter the end cap and the spring can operate to control oil flow responsive to a pressure differential across the end cap.